Transmission electron microscope (TEM) tomography provides three-dimensional images at the nanometer scale. It is a mainstream technique in biological electron microscopy, and is rapidly finding applications in the semiconductor and nanotechnology industries. In biology, scientists are interested in producing faithful tomograms of frozen-hydrated samples, since specimens prepared in this way are considered to represent the native in vivo structure. In the case of typical mammalian cells and tissue, such specimens are usually high- pressure frozen, and then prepared for electron tomography using cryo-ultramicrotomy. However the difficulties of cryo-ultramicrotomy, and the artifacts that are unavoidably created by mechanical sectioning, have discouraged most laboratories from attempting study of frozen-hydrated cells and tissue by electron tomography. Preliminary work by our Wadsworth collaborators has shown that use of a cryo-FIB system avoids the artifacts and difficulties of cryo-ultramicrotomy, and offers additional advantages in preparing frozen-hydrated specimens. PUBLIC HEALTH RELEVANCE: This proposal will develop tools that allow biologists to get a clearer picture of the structure and function of the cell. This knowledge is fundamental to innumerable areas of medical research and practice.